The present invention relates to an electrical connector usable with a variety of electrical devices. More specifically, the present invention relates to a composite, one-piece electrical connector having an end which is crimpable and another end which is suitable for a mechanical connection.
Electrical connectors are devices designed to mechanically connect together electrical components. An electrical connector is not limited to any one engineering design, but rather, based on desired features, can take on any one of a variety of shapes and designs.
One conventional type of an electrical connector, is used to connect flexible insulated electrical conductor wires or cables to the terminals of electrical devices such as transformers. Such a connector is commercially manufactured having a crimpable end and another end which is suitable for mechanical connection. The crimpable end generally contains a cavity designed to accommodate a conductive portion of the electrical conductor wire. The end suitable for mechanical connection generally contains a threaded hole designed to accommodate a threaded electrical device such as a probe portion of a transformer. The connector hole, which need not be threaded, usually extends transversely into one end of the connector. The connector cavity, located at the other end of the connector, is usually cylindrical in shape. The cavity usually has an axis which is substantially co-linear with the connector axis, and the cavity usually extends into the body of the connector sufficiently far to accommodate an effective length of a conductive portion of the conductor wire.
The above-mentioned probe is usually made of a metal alloy which is almost always different from the metal alloy which makes up the conductive portion of the conductor wire. For example, present economics dictate that these conductive portions of conductor wire are usually made of aluminum or aluminum alloys. However, the probe is generally made of copper or copper alloys because the probe usually must make contact with a receptacle or terminal, generally made from copper or copper alloys.
Those skilled in the art know that a composite terminal, made of dissimilar metal alloys metallurgically bonded together along a bonding interface, is susceptible to undesirable metallic diffusion or formation of intermetallic compounds at the bonding interface when the composite terminal is heated to elevated temperatures. Moreover, an additional problem that can result is severe electrical resistance to current flow, or loss of bond strength, or both along the bonding interface.
It also can be appreciated by those skilled in the art that during its course of operation, the conventional connector described above can often be subjected to repeated thermal cycles wherein it is caused to alternately heat up and cool off. For example, the connector may heat up to approximately 80 Centrigrade degrees (144 Fahrenheit degrees) above its surrounding temperature before it cools off. This thermal cycle is an important design consideration for electrical connectors because aluminum (or aluminum alloys) and copper (or copper alloys) have different coefficients of thermal expansion. As such a connector experiences such a thermal cycle, stresses build up with the result being that an electrical failure may be induced either in the hole-containing end where the probe makes contact or in the cavity-containing end where the conductive portion of the conductor wire makes contact. Therefore, to avoid thermally-induced electrical failures in such a type of conventional connector, it is desirable to mechanically affix the probe and the conductive portion of the conductor to the connector.
Such a conventional connector, therefore, should be sufficiently hard at one end to receive a probe portion, usually threaded, and it should be sufficiently soft at the other end to be crimpable over a conductive portion of a conductor wire. Such a conventional connector also should be able to function well in a thermally cycling course of operation.
In such a conventional connector, the end having the transverse hole is usually made of a hard or hardenable metal alloy because it is undesirable to have metal deformation take place in the hole-containing end of the connector as a result of thermally induced stresses. Also, because it is desirable to crimp the cavity-containing end after an effective length of the conductive portion of an electrical conductor has been inserted within the cavity, the end of such a conventional connector (having a cylindrical cavity) is usually made of a soft or softenable metal alloy. Currently manufactured one-piece, connectors present a compromise situation with respect to selection of a desired combination of mechanical properties suitable for a crimpable end and for a mechanical connection end. If the connector is made entirely of one relatively soft malleable metal or one metal alloy suitable for crimping, unacceptable deformation and eventual failure will occur at the hole-containing end of the connector. If the metal or alloy is entirely hard, unacceptable build-up of a highly electrically resistant film and eventual failure will occur at the cavity-containing end of the connector.
One attempt to meet materials of construction demands of electrical connectors has resulted in a patent (U.S. Pat. No. 3,876,280) being issued for a bimetallic connector, fabricated from dissimilar metals. This patent specifically teaches that dissimilar metals must be used and contemplates a special process for joining such dissimilar metals. This process relies upon a solid state bonding process to join the two dissimilar metals together and thus presents several production line problems. For example, the solid state bonding process requires that, prior to being joined together along a bonding interface, the dissimilar metals have an extremely flat surface and be extremely clean. Fine grinding techniques have to be used to achieve these flat surfaces. In addition, the solid state bonding process requires that the metals be joined together, at their bonding interface, no more than five minutes after having been finely ground and cleaned. These requirements put undue strain upon most conventional bimetallic connector manufacturing processes.
It is an object of the present invention to provide a novel, one-piece, composite electrical connector having one end portion which is relatively soft and crimpable and another end portion which is relatively hard and suitable for mechanical connection.
It is also an object of the present invention to provide a novel, one-piece, composite electrical connector as set forth above which can be manufactured using conventional welding techniques.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings.